Hot to Trot

Principles and practices for running in the heat

might be good advice for cooks and politicians, but for runners, it just doesn’t work.

Many major, "can’t miss" events are scheduled during the hottest times of the year, with this year’s Olympic marathons in Athens perhaps the highest profile to be held under blazing temperatures. While optimum performance comes under cooler conditions, runners are like mad dogs and Englishmen and insist on racing in the midday sun. Given that many will either elect to do so, or, like the Olympic marathoners, have no choice in the matter, what are the best strategies and techniques for running in the heat?

The acknowledged expert in the field is Dr. David Martin (Senior Sports Physiologist, Australian Sports Commission), whose research on the effects of heat on exercise goes back to when athletes were preparing for the hot and humid 1996 Atlanta Olympics.

"The number one principle to remember is that you cannot accumulate heat," Martin says. Research has shown that the enzymes that produce muscular energy function best around 101 degrees, but go much greater than 104 or 105, and they don’t work at all. "We live and exercise very close to the survival edge," says Martin. During exercise, 40 percent of the muscles’ effort produces work, with the remainder simply generating body heat. For example, running at 7:30 pace produces 12 times more heat than sitting in a lawn chair sipping a cool drink. "That’s fine on a cool day," says Martin, and it’s what makes running possible even in near-Arctic conditions. "But when the weather gets warm, you have to get rid of that heat to continue to exercise effectively."

The body must dissipate this rising internal furnace, and the most effective way to do that is through evaporation of perspiration. Of course, the fluid for that sweat has to come from somewhere, and it’s drawn from the blood plasma, which makes the blood thicker and more sluggish as it tries to supply the working muscles.